Help: clarify description of list(INSERT)

Since the argument is called 'index', use that in the description.

Help/command/list.rst

@@ -152,7 +152,7 @@ For more information on regular expressions look under
 
   list(INSERT <list> <element_index> <element> [<element> ...])
 
-Inserts elements to the list to the specified location.
+Inserts elements to the list to the specified index.
 
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